11 fascinating sunfish facts

11 fascinating sunfish facts

Te Papa recently received a rare sunfish specimen from Auckland Museum, so we decided to find out more about these mysterious ocean-dwelling animals. Here are our fascinating facts:

1.Sunfish don’t have a tail! Some people call them a ‘gigantic swimming head’ (which seems a bit rude). Instead of a tail their dorsal and anal fins are fused together into a rudder-like structure called a clavus. The sunfish swims by flapping its dorsal and anal fins synchronously, like oars.

This is a common sunfish, also called an ocean sunfish, Mola mola. Our specimen is the rarer sharp-tailed sunfish, Masterus lanceolutus.

There are four species of sunfish: common sunfish (Mola mola), slender sunfish (Ranzania laevis), sharp-tailed sunfish (Masterus lanceolutus) and southern ocean sunfish (Mola ramsayi). The species at Te Papa is a sharp-tailed sunfish. Scientists know the most about the common sunfish, so we’re pretty excited to be able to find out more about the rare sharp-tailed sunfish.

Sunfish are the heaviest bony fish species alive today. Common sunfish weigh around a metric tonne on average. The biggest common sunfish ever caught weighed over two metric tonnes!

Sunfish eat jelly (but no ice cream). We think they eat jelly-like small gelatinous animals (including jellyfish) but are known to also snack on algae, crustaceans, and small fishes if the opportunity presents itself. We’re not sure what our specimen has been eating, so we’re going to open it’s stomach to find out!

Scaly? I don’t think so! Sunfish have a tough, elastic skin which is covered in mucus. Delightful.

Playing dead: sometimes sunfish appear to be dead, floating on their side at the ocean surface. Don’t worry! The sunfish (generally) aren’t dead, but scientists don’t know why they do this. It could help the sunfish to warm up from their deep-water dives in search of prey. Or it could be an opportunity for the sunfish to engage the services of a cleaner fish to remove the huge numbers of parasites they harbour.

Mistaken identity: Sunfish can also be seen swimming slowly along with their dorsal fin sticking out of the water causing some people to think it’s a shark!

Big? Yes. Dangerous? No. Despite their size, sunfish don’t pose a threat to humans, although given the jaw muscles and teeth fused into something like an industrial bolt cutter, you don’t want to go putting your fingers anywhere near the mouth. We pose more of a threat to the sunfish, mainly through the fishing industry. Although sunfish aren’t good to eat, they comprise a large proportion of bycatch in fisheries in the Atlantic and Pacific oceans.

Te Papa’s scientists will be conducting research on our sunfish specimen on 13 August 2013. We’ll be live-blogging and sharing the scientists’ findings through Facebook and Twitter. It’s a fantastic opportunity to sit in as scientists do their research on these rarely seen animals. Don’t miss out!

Stay tuned this week for more blogs about the amazing sunfish. You can find out more about sunfish and learn what Te Papa will do with the sunfish once the scientists have completed their research.